\begin{tikzpicture}[scale=1, every node/.style={transform shape}]
	% piezo
	\draw (0,0) node[rground] {}
				to[piezoelectric, l=$X$] (0,2) to (2,2)
				to[R, l=$R_x$, *-] (2,0) node[rground] {};
				
	% diodes
	\draw (2,2) to[R,l=$R$, -*] (5,2);
	\draw (5,0) node[rground] {}
				to[sDo, l_=$D_2$] (5,2)
				to[sDo, l_=$D_1$] (5,4)
				node[vcc] {$V_{cc}$};
	\draw (5,2) to[short, -o] (6,2)
				node[right] {$V_o$};
	
	% opamp
	\iffalse
	\draw (9,2.5) node[op amp] (comp) {};
	\draw (comp.-) to ++(0, 0.5) node[vcc] {$V_{ref}$};

	\draw (comp.+) to[R, l=$R_A$] ($(comp.+) + (-2.5, 0)$) -| (5,2);
	\draw (comp.+) |- (8,0) to[R, l=$R_F$] ++(2,0) -| (comp.out)
					to[short, -o] ++(1,0) node[right] {$V_o$};
	\fi
\end{tikzpicture}